1. Field of the Invention
The present invention relates to a blind rivet disassembling device and method and a production system using the method, wherein a blind rivet body having a body portion and a flange portion, with a through hole being formed through the blind rivet body in an axial direction of the body portion from the body portion toward the flange portion, is inserted into clamping holes formed in base metals, a mandrel having a stem portion and a head portion, the head portion being substantially integral with the stem portion and larger than the diameter of the through hole of the blind rivet body, is inserted into the through hole, the head portion of the mandrel is pulled into the through hole as the mandrel is pulled, so that a peripheral wall of the body portion around the through hole undergoes a plastic deformation and is bulged and the mandrel is broken, allowing a portion of the mandrel to remain as a residual mandrel within the through hole, the base metals are sandwiched by the bulge of the peripheral wall of the body portion and the head portion of the mandrel, and the blind rivet clamped to the base metals is separated from the base metals.
2. Description of the Related Art
As a technique for joining base metals such as steel plates or plastic plates or for joining another member to such a base metal there is known a rivet clamping technique. As an example there is known a clamping method in which base metals 1 and 2 are joined mechanically with use of a blind rivet.
As shown in FIG. 14(a), the blind rivet, indicated at 10, comprises a blind rivet body 11 and a mandrel (core stem) 12. The blind rivet body 11 comprises a body portion 11b and a flange portion 11c which is substantially integral with the body portion 11b. A through hole 11a is formed through the blind rivet body 11 in an axial direction of the body portion 11b from the body portion toward the flange portion 11c. The mandrel 12 comprises a head portion 12a and a stem portion 12c which is substantially integral with the head portion. The head portion 12a has an outside diameter larger than the diameter of the through hole 11a. The stem portion 12c is formed with a constriction 12b at an intermediate position in its extending direction.
Using the blind rivet 10, the base metals 1 and 2 are clamped together mechanically in accordance with the following procedure for example.
First, the body portion 11b of the blind rivet body 11 is inserted into clamping holes 1a and 2a of base metals 1 and 2, as shown in FIG. 15(a), and a blind rivet clamping device 13 is set at an end portion of the mandrel 12, as shown in FIG. 15(b),
Then, as shown in FIG. 15(c), a nose piece 13a of the blind rivet clamping device 13 is brought into close contact with the flange portion 11c of the blind rivet body 11 and the blind rivet clamping device 13 is triggered while the flange portion 11c is pushed against the base metal 1 by the nose piece 13a.
As a result, the mandrel 12 is chucked by a jaw member 13b of the blind rivet clamping device 13 and is pulled in the direction opposite to the pushing direction, then as the head portion 12a of the mandrel is pulled into the through hole 11a, the peripheral wall of the body portion 11b projecting from the back side of the base metal 2 is deformed plastically into a bulge 11d by the head portion 12a of the mandrel 12, which is brought into pressure contact with the base metal 2.
In this state, if the jaw member 13b is further pulled in the direction opposite to the pushing direction, the mandrel 12 will be broken at its constriction 12b, so that the base metals 1 and 2 are clamped together by the blind rivet 10, as shown in FIG. 15(d). A portion of the mandrel 12 remains as a residual mandrel 12' within the through hole 11a, as shown in FIG. 14(b).
According to this method using the blind rivet 10, since the base metal clamping is effected by applying tension in the direction opposite to the pushing direction, as shown in FIGS. 15(a) to 15(d), the clamping work for the base metals 1 and 2 can be done without supporting the back side of the base metals and therefore this method is suitable for clamping the base metals 1 and 2 in such a place where the worker's hand cannot reach the back side of the base metals.
Thus, in the blind rivet 10, as the mandrel 12 inserted into the through hole 11a of the blind rivet body 11 is pulled, the peripheral wall of the body portion undergoes a plastic deformation, with consequent formation of the bulge 11d, and the base metals 1 and 2 are held in a clamped state by both bulge 11d and flange portion 11c. In the event there should occur a defective clamp in clamping the blind rivet 10 to the base metals 1 and 2 and the resulting necessity of repeating the same work or in the event there should occur the necessity of recycling the base metals 1 and 2, it is necessary to disassemble and remove the blind rivet 10.
As a disassembling method for the blind rivet 10 there is known such a method as shown in FIG. 16, in which with a drill 14, the flange portion 11c of the blind rivet 10 is cut and removed from the body portion 11b, then, by tapping the cut portion in a direction in which the body portion 11b comes out of the clamping holes 1a and 2a, the blind rivet 10 is pulled out from the base metals 1 and 2.
Such a conventional blind rivet disassembling method requires much time and labor for preparatory works, including selection of the drill 14 and the cutting work. Moreover, in cutting the flange portion 11c, if the tip of the drill 14 reaches the base metal 1 and cuts the clamping hole 1a of the base metal, with consequent increase in size of the clamping hole 1a, as shown in FIG. 17, it will be impossible to ensure a sufficient clamping force even if this base metal 1 is recycled and re-clamped using the blind rivet 10. Generally, once the base metals 1 and 2 are flawed in the blind rivet disassembling work, it becomes difficult to recycle such base metals.
Further, in the case of using this type of a drill in the clamp member disassembling work, the blind rivet body 11 undergoes a follow-up rotation with rotation of the drill 14 at the time of cutting the flange portion 11c of the blind rivet 10, thus giving rise to the problem that the base metal 1 is scratched or it is impossible to cut the flange portion 11c. Particularly, when the base metal 1 is used as an outer component of a product, a scratch, if any, on the surface of the base metal 1 will markedly deteriorate the commercial value of the product. Therefore, such a scratched base metal 1 cannot be recycled, and if it should be recycled, the percent defective of the base metal at the time of disassembly would become very high.
Therefore, to prevent the follow-up rotation of the clamp member with rotation of the drill 14, the flange portion 11c is cut with by the drill 14, as shown in FIG. 16, while the flange portion 11c or the body portion 11b is chucked by a chucking tool 15 such as pliers or pincers. However, this work is performed by two or more workers because it is dangerous if this work is done by one worker, resulting in an increase of personnel expenses in the disassembling work.
Particualarly, as shown in FIG. 18, when the flange portion 11c of the blind rivet 10 is in a flat shape and is difficult to be chucked by the chucking tool 15 and when the base metals 1 and 2 are clamped by the blind rivet 10 in such a place where the worker's hand cannot reach the back side of the base metals, it is difficult to prevent the follow-up rotation because the body portion 11b cannot be chucked by the chucking tool 15.
As another method for removing the blind rivet 10 from the base metals 1 and 2 there also is known a method in which the flange portion 11c of the blind rivet 10 and the body portion 11b are cut from each other while nipping the flange portion 11c by a cutting tool such as a nipper. According to this method, the follow-up rotation of the blind rivet 10 can be prevented at the time of cutting the flange portion 11c and the body portion 11b from each other, so that the inconveniences encountered in the disassembling method using the drill 14 can be eliminated.
However, in the blind rivet 10, as shown in FIG. 14(b), its body portion 11b is deformed plastically by the head portion 12a of the mandrel 12 and is caulked to the base metals 1 and 2, the mandrel 12 is formed using a material of a higher hardness than the hardness of the body portion 11b in order to cause a plastic deformation of the mandrel 12, and in a clamped state of the blind rivet 10 to the base metals 1 and 2 a portion of the mandrel 12 remains as the residual mandrel 12' within the through hole 11a.
Therefore, in the method wherein the body portion 11b of the blind rivet 10 is nipped by such a cutting tool as a nipper and in this state the flange portion 11c and the body potion 11b are separated from each other, a cutting edge of the cutting tool may come into abutment against the residual mandrel 12' remaining in the through hole 11a of the blind rivet body 11 at the time of cutting the body portion 11b and this abutment may inhibit the cutting work by the cutting tool.
In this case, if an attempt is made to cut the residual mandrel 12' forcibly, a large cutting force is required for cutting the flange portion 11c and there is a fear that the cutting edge of the cutting tool may be damaged.
For separating the flange portion 11c and the body portion 11b from each other while avoiding cutting of the residual mandrel 12', there is adopted a method in which the body portion 11b and the flange portion 11c are cut from each other while the position of contact of the cutting edge relative to the periphery of the body portion 11b is changed into the circumferential direction. However, this cutting method is disadvantageous in that much time and labor are required for the cutting work because the separation of the body portion 11b and the flange portion 11c cannot be done by a single cutting operation.
If the residual mandrel 12' remaining in the through hole 11a of the blind rivet body 11 is short and is present on only the body portion 11b side with respect to the cut position between the flange portion 11c and the body portion 11b and if the cutting edge of the cutting tool does not come into abutment with the residual mandrel 12' in the cutting work, the flange portion 11c and the body portion 11b can be cut from each other in a relatively easy manner even by the use of the above type of a cutting tool.
However, even if the flange portion 11c and the body portion 11b are cut from each other by the cutting tool, since the body portion 11b of the blind rivet 10 bites into and is caulked to the base metals 1 and 2 by the residual mandrel 12', it is necessary to perform a secondary work of tapping the blind rivet body 11 from the base metal 1 side after separation of the flange portion 11c and pulling out the blind rivet body 11 from the clamping holes 1a and 2a of the base metals 1 and 2.